diff --git a/src/renderers/shaders/ShaderChunk/lights_lambert_vertex.glsl b/src/renderers/shaders/ShaderChunk/lights_lambert_vertex.glsl
index 1b4b80a163b6910abcac28dd2ac24acaf904d6ca..89fb25924aedc51deb118252ae13b5fd9fc4ada9 100644
--- a/src/renderers/shaders/ShaderChunk/lights_lambert_vertex.glsl
+++ b/src/renderers/shaders/ShaderChunk/lights_lambert_vertex.glsl
@@ -3,6 +3,11 @@ vec3 diffuse = vec3( 1.0 );
 GeometricContext geometry = GeometricContext( mvPosition.xyz, normalize( transformedNormal ), normalize( -mvPosition.xyz ) );
 GeometricContext backGeometry = GeometricContext( geometry.position, -geometry.normal, geometry.viewDir );
 
+	vLightFront = vec3( 0.0 );
+#ifdef DOUBLE_SIDED
+	vLightBack = vec3( 0.0 );
+#endif
+
 #if MAX_POINT_LIGHTS > 0
 
 	for ( int i = 0; i < MAX_POINT_LIGHTS; i ++ ) {
@@ -94,4 +99,4 @@ GeometricContext backGeometry = GeometricContext( geometry.position, -geometry.n
 
 		#endif
 
-	}
\ No newline at end of file
+	}